Topband: Skywaves from Monopole Surface Waves

[Tom W8JI]

> The measured fields by the consultant show that no "notch" exists in the 
> elevation pattern of that monopole from 0-3 degrees.  Nor would one appear 
> in the elevation pattern of ANY monopole up to 5/8-wave in height.


Anyone who drives away from an AM BC station would quickly realize the field 
continues for a very long distance and is not that much weaker than direct 
wave until we get a fair distance out, perhaps 10-20 km for a few dB down 
from direct wave.

This is pretty old stuff.

The misconception comes from EZNEC and other programs that calculate pattern 
at many wavelengths away from the antenna over flat earth.

On several occasions the author of EZNEC told me he never wanted to include 
TOA in his program because it would be misused. Since a competing program 
had it, he reluctantly included it. I may be mistaken, but I think he 
mentioned EZNEC calculated pattern at 50 or 100 wavelengths, not infinite 
distance.

73 Tom